Reading a Tracert Report

Posted on 2001-06-18
Last Modified: 2012-05-04
I'm only asking in this area cuz I'm figuring folks here have deepest expertise regarding internet connectivity issues.

I'm running a dedicated Win2K box hosted by a Web Service Provider. I've had a couple clients who have experienced extreme lag lately and have asked them for a tracert. (below).

I don't know how to read tracert reports well enough to be 100% certain that I'm getting reliable information from the folks that host my site...though I have no outstanding complaints about them...I just want verification of what I'm being told.

As they read this trace report they tell me the bottleneck is at AmeriTech.

Resolving DNS hostname www.TTSTRAIN.COM. Please wait...
Trace Route (Results logged to file: SYS:\ETC\IPTRACE.LOG)
Max Hops: 30 Max Wait: 5 seconds Dest Port: 40001
Hop          RTT       IPAddress
  1        2.000ms (HOSTNAME UNKNOWN)
  2        5.009ms (BAS0-0.CHICAGO.IL.AMERITECH.NET)
  3        6.000ms (FA3-1-CORE0.CHICAGO.IL.AMERITECH.NET)
  4     3960.006ms (LOOPBACK)
  5       65.000ms (www.TTSTRAIN.COM)

The thing that looks a like strange to me is that I'm used to seeing the last hop or two as internal to my provider...inside thier domain mask (i'm betting I'm displaying a fair bit of ignorance with my termonology.) Here's the end of a tracert from my own connection:

17   200 ms   201 ms   200 ms []
18   260 ms   201 ms   200 ms []
19   210 ms   200 ms   201 ms
20   210 ms   190 ms   211 ms

I've never experienced the sort of lag that my client the problem _probably _is not with my host...but I'd like to be 100% I'm doing everything I can.

Question by:juststeve
LVL 17

Expert Comment

ID: 6203356
Line number 4 says 3960ms on Loopback? Is that correct? Someones routing isn't correct and this is why they are having problems. You should never see the loopback in a trace route unless someones routing is goofy!

Expert Comment

ID: 6203834
I ran a tracert on the site from my location. There were no problem with the tracert. You should never see a loopback address in a tracert. It looks as if there was a routing table problem, but that it has now been cleared.

Author Comment

ID: 6203911
When I work backwards...sending a tracert from my server to the client's address I'm getting consistant and constant 'Request Timeouts' at:
16   220 ms   220 ms   221 ms  193.ATM7-0.GW7.PHL1.ALTER.NET []
17   250 ms   281 ms   250 ms []
18     *        *        *     Request timed out.
[more clipped]

This is going on more than a week with this problem.

So it seems as though the original tracert from the client folded those timeouts into a loopback...for whatever reason. It appears my host is on the level and that we have to figure out how to shake the tree at Yes?

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LVL 17

Expert Comment

ID: 6203957
Yes, if a route can't find it's destination sometimes Admins will send it to the loopback to keep it alive until it goes thru the routing table again until finally reaching it's destination. In this case it sounds like there is a bad route. I would go to them and have them correct this in their routing table. You also normally only see this when people start putting some static routes in the router. Static takes precedence over dynamically learned routes.

Author Comment

ID: 6204542
bbast...I'm curious about the phrase...'It looks as if there was a routing table problem, but that it has
now been cleared. '

Though you mention 'it looks as though the problem's been cleared' things are reporting to my tracert exactly as they've been for the duration of the problem.

any clarifications are much appreciated.

LVL 79

Accepted Solution

lrmoore earned 50 total points
ID: 6204558
A router's address that it is known by, or it's "handle" if you will, is the highest address assigned to any interface -- unless there is a loopback address assigned. It looks like somebody goofed up and put a loopback interface on a router with the ip address of, the same as the loopback interface address on every PC in the world. It's no wonder the packet gets bounced back and forth in a traceroute, but should be OK otherwise...
Ping times to are all <90 ms from me..

You will see in this trace "loopback0.core1.Atlanta...." One more pointer to someone setting that looback address to -- big time no no on the router...


Tracing route to over a maximum of 30 hops

  1    16 ms    15 ms   <10 ms []
  2   <10 ms    15 ms    16 ms
  3    15 ms    16 ms    31 ms
  4    31 ms    32 ms    31 ms []
  5    16 ms    31 ms    31 ms
  6    15 ms    32 ms    31 ms []
  7    15 ms    32 ms    31 ms [
  8    16 ms    31 ms    31 ms []
  9    32 ms    31 ms    63 ms []
 10    78 ms    78 ms    94 ms []
 11    78 ms    79 ms    78 ms []
 12    78 ms    94 ms    93 ms []
 13    78 ms    94 ms    78 ms []
 14    78 ms    94 ms    94 ms []
 15    78 ms    94 ms    94 ms
 16    78 ms   109 ms    94 ms

Trace complete.

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